A comparison of ether- and alkyl-derivatized imidazolium-based room-temperature ionic liquids: a molecular dynamics simulation study.
Molecular dynamics simulations of ether-derivatized imidazolium-based room-temperature ionic liquids (EDI-RTILs), [C(5)O(2)mim][TFSI] and [C(5)O(2)mim][BF(4)], have been performed and compared with simulations of alkyl-derivatized analogues (ADI-RTILs). Simulations yield RTIL densities, self-diffusion coefficients and viscosity in excellent agreement with experimental data. Simulations reveal that structure in the EDI-RTILs, quantified by the extent of nanoscale segregation of tails as well as cation-ion and cation-cation correlations, is reduced compared to that observed in the ADI-RTILs. Significant correlation between ether tail oxygen atoms and imidazolium ring hydrogen atoms was observed in the EDI-RTILs. This correlation is primarily intramolecular in origin but has a significant intermolecular component. Competition of ether oxygen atoms with oxygen atoms of TFSI(-) or fluorine atoms of BF(4)(-) for coordination of the ring hydrogen atoms was found to reduce the extent of cation-anion correlation in the EDI-RTILs compared to the ADI-RTILs. The reduction in intermolecular correlation, particularly tail-tail segregation, as well as weakening of cation-anion specific interactions due to the ether tail, may account for the faster dynamics observed in the EDI-RTILs compared to ADI-RTILs.
Smith
Grant D
GD
Department of Materials Science and Engineering, University of Utah, 122 S. Central Campus Drive, Salt Lake City, UT 84112, USA.
Borodin
Oleg
O
Li
Liyong
L
Kim
Hojin
H
Liu
Qin
Q
Bara
Jason E
JE
Gin
Douglas L
DL
Nobel
Richard
R
D000473:Alkanes / Q000737:chemistry*; D003198:Computer Simulation; D004058:Diffusion; D004987:Ethers / Q000737:chemistry*; D007093:Imidazoles / Q000737:chemistry*; D052578:Ionic Liquids / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D010100:Oxygen / Q000737:chemistry; D011789:Quantum Theory; D013816:Thermodynamics; D014783:Viscosity
D000473:Alkanes; D004987:Ethers; D007093:Imidazoles; D052578:Ionic Liquids; D010100:Oxygen